Social inequalities in health determine the risk of morbidity and mortality from childhood through to adult life(Reference Mackenbach, Stirbu and Roskam1). Consistent evidence indicates that people of low socio-economic status (SES) have a heavier burden of disease than their better-off counterparts(Reference Mackenbach and Kunst2). SES refers to an individual's relative position in the social hierarchy and can be operationalized through diverse indicators including educational attainment, occupation and/or income. It is possible that such indicators affect food consumption in different ways due to different underlying social and psychological processes involving factors like nutritional knowledge, budget constraints or peer group behaviour(Reference Turrell, Hewitt and Patterson3, Reference Galobardes, Lynch and Smith4). Diet quality has been shown to follow a socio-economic gradient(Reference Darmon and Drewnowski5). Studies examining the impact of SES on adolescents' and children's food intake have suggested high consumption of high-fat and high-sugar foods, and low consumption of fruits and vegetables, in individuals from disadvantaged groups(Reference Sausenthaler, Kompauer and Mielck6–Reference Eloranta, Lindi and Schwab10).
Family structure and support is one of the most influential aspects of the social environment of children. Parental influences on children's food choices and intake have an effect on individual and family practices, and operate among other mechanisms via availability and accessibility of foods or parental eating behaviour as food modelling(Reference Vereecken, Keukelier and Maes11, Reference Hebestreit, Keimer and Hassel12). Through this link, parental educational level is associated with children's food intake and frequency of consumption, and subsequently with childhood overweight and obesity(Reference Lamerz, Kuepper-Nybelen and Wehle13–Reference Cooke, Wardle and Gibson15). However, the stability and repeatability of these relationships between countries have been scarcely investigated.
The present study aimed to assess the association between parental education levels and the consumption frequency of obesity-related food groups (e.g. foods that are shown by consistent evidence to be related, either positively or negatively, to overweight and obesity in children) among children aged 2 to 9 years from eight European countries.
Methods
The ‘Identification and prevention of Dietary- and lifestyle-induced health EFfects In Children and infantS’ (IDEFICS) study is a population-based multicentre study of children aged 2 to 9 years from eight European countries. The two main aims were: (i) to investigate the aetiology of obesity and related disorders; and (ii) to implement a community-based intervention to prevent obesity and related diseases. For the present analysis, children recruited during the cross-sectional baseline survey were considered. Between September 2007 and May 2008, 31 543 children from primary schools and pre-schools of selected regions in Italy (Avellino), Estonia (Tartumaa, Harjumaa), Cyprus (Nicosia District, Paphos), Belgium (East-Flanders), Sweden (Västra Götaland), Hungary (Baranya, Zala), Germany (Lower Saxony) and Spain (Zaragoza, Huesca) were invited to participate in the baseline survey (T0) with a response rate of 53·4 % (n 16 864). The lowest response rates were reached in Spain (41 %) and Hungary (44 %), and the highest in Italy (60 %) and Sweden (66 %). In total 16 224 children (51·4 %) fulfilled the study's inclusion criteria (complete information on age, sex, height and weight). Sample size ranged from 1507 in Spain to 2567 in Hungary. An in-depth description of the complete IDEFICS study population is given by Ahrens et al.(Reference Ahrens, Bammann and Siani16). Of the total sample, 14 426 children (88·9 %) had valid data on SES and food intake, and were included in the current analysis. Further information on the study procedures is available in previous papers(Reference Ahrens, Bammann and de Henauw17, Reference Bammann, Peplies and Pigeot18). Each participating centre obtained ethical approval for the study from its respective responsible authority. All children provided oral consent and their parents provided written informed consent for all examinations and the collection, analysis and storage of personal data and collected samples.
Measurements
Data on personal, social, environmental and behavioural factors were collected by means of two standardized self-administered questionnaires that were filled in by the parents or guardians of the child. Education level of parents taken from the core parental questionnaire was used as a proxy indicator of SES, using categories according to the International Standard Classification of Education (ISCED)(19). Three levels of education (low, medium, high) were created out of the six ISCED levels of the parental questionnaire: ISCED level 0, 1 or 2 adding up to low education; level 3 or 4 adding up to medium education; and level 5 or 6 adding up to high education. For the purposes of the present analysis, the highest education level of parents (either mother or father) was considered.
Dietary data were obtained by the food frequency section of the Children's Eating Habits Questionnaire–Food Frequency Questionnaire (CEHQ-FFQ)(Reference Huybrechts, Bornhorst and Pala20) in which the frequency of the child's consumption of selected food items during the preceding four weeks was reported. In order to assess meals under parental control, recall referred to meals outside the school canteen or childcare meal provision settings only(Reference Huybrechts, Bornhorst and Pala20, Reference Lanfer, Hebestreit and Ahrens21). The CEHQ-FFQ consisted of forty-three food items clustered into fourteen food groups. It was applied as a screening instrument to investigate the consumption of foods shown to be related, either positively or negatively, to overweight and obesity in children. The CEHQ-FFQ was not designed to provide an estimate of total energy intake or total food intake, but rather to investigate the consumption frequency of obesity-related foods. Those foods less likely to be associated with obesity were not included. Response options displayed were as follows: ‘never/less than once a week’, ‘1–3 times a week’, ‘4–6 times a week’, ‘1 time per day’, ‘2 times per day’, ‘3 times per day’, ‘4 or more times per day’ and ‘I have no idea’. For the analysis, a conversion factor was used to transform the questionnaire answers into actual weekly consumption frequencies. When the proxy reported having ‘no idea’, consumption frequency could not be calculated and the data were not used in the analysis of the respective food item. No information on portion sizes was obtained.
Anthropometric measurements were carried out by trained staff following a standardized procedure in all centres. Body height (cm) was measured without shoes and all braids undone using a portable stadiometer (SECA 225). Weight (kg) was measured by means of a child-adapted version of an electronic scale (TANITA BC 420 SMA) with the children in a fasting status and wearing only underwear(Reference Stomfai, Ahrens and Bammann22). BMI was calculated and categorized following cut-off points according to the criteria of the International Obesity Taskforce(Reference Cole, Bellizzi and Flegal23, Reference Cole, Flegal and Nicholls24). The sample was classified into thinness, normal weight, overweight and obese categories.
Statistical analysis
Descriptive data are shown as proportions, means and standard deviations. Differences in frequency of food consumption (times/week) by classified parental education (low, medium and high) were assessed by analysis of covariance models. Logistic regression analysis was used to examine the effect of parental education on frequency of food consumption. For this purpose, frequencies of food consumption were divided into tertiles (lowest, middle and highest consumption), based on country-specific variable distributions and for each food item separately. Finally, dichotomous variables were created, comparing the highest consumption (high consumers) against the rest of the sample, namely the lowest and middle tertiles (average consumers). High parental education level was set as the reference category. Prevalence of high consumers by parental education was also calculated. Both analyses (analysis of covariance and logistic regression) were adjusted for the following covariates: sex, age, BMI category and country. Statistical significance was set at P ≤ 0·05. All analyses were conducted using the Predictive Analytic Software (PASW) version 18·0 (SPSS Inc., Chicago, IL, USA).
Results
Study participants excluded from the present study did not differ from those included in terms of sex, age, BMI category or parental education level. Based on the statistically significant interaction between educational level and country (all P < 0·001), results are provided for the whole sample and by country. Table 1 describes the sociodemographic and anthropometric characteristics of the participating children (n 14 426). Mean age was 6·0 (1·8) years, with 46·6 % being of pre-school age (<6 years old) and 50·9 % being girls. Of the children, 69·8 % had normal weight for their height and age, while 12·4 % were classified as overweight and 6·8 % as obese. Some 41·2 % of the participants’ parents had a high education level, 50·1 % a medium education and 8·7 % a low education. Sample size as a proportion of the total population varied among countries from 8·8 % in Spain to 17·2 % in Hungary. The following results refer to meals consumed outside the school canteen or childcare meal provision settings. The percentage of meals under parental control differed between countries (Italy 88 %, Estonia 69 %, Cyprus 84 %, Belgium 77 %, Sweden 65 %, Germany 90 %, Hungary 69 % and Spain 84 %).
Table 1 Characteristics of the study sample: children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Table 2 shows the weekly consumption frequencies and odds ratios (95 % confidence intervals) for consumption of low-sugar and low-fat foods by parental education level for the total sample. Significant differences in mean frequency of consumption of the chosen foods between parental education groups were observed. The highest mean frequency of weekly consumption for vegetables, fruits, pasta/noodles/rice, wholemeal bread and water was observed in the highest education level category. The largest differences were found for water (21·6 (se 0·1) times/week in the high category v. 19·5 (se 0·3) times/week in the low category) and vegetables (9·0 (se 0·1) times/week in the high category v. 7·7 (se 0·2) times/week in the low category). No significant trend was found for plain unsweetened milk. Taking into account the odds ratio results, children with parents in the low and medium parental education level groups had lower odds of more frequently eating vegetables, fruits, pasta/noodles/rice and wholemeal bread (P < 0·001). Children with parents from the low parental education level group had also lower odds of more frequently drinking water (P < 0·05) and plain unsweetened milk (P < 0·001). The largest odds ratio differences were found in the low category (reference category: high) for vegetables (OR = 0·56; 95 % CI 0·47, 0·65) and fruits (OR = 0·56; 95 % CI 0·48, 0·65).
Table 2 Weekly consumption frequency (means and their standard errors), prevalence of high consumption, and odds ratios (95 % confidence intervals) for intake of low-sugar and low-fat foods by classified parental education level; children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Reference group: high education.
Analysis of covariance model adjusted for gender, age and BMI category. Two-sided level of significance (P < 0·05): asignificant difference between low and medium; bsignificant difference between low and high; csignificant difference between medium and high.
OR and 95 % CI determined by logistic regression models. Variables included in the models were parental education, gender, age and BMI category. Two-sided level of significance: *P < 0·05, ***P < 0·001.
†p refers to the proportion of participants assigned to the highest consumption category.
Table 3 shows the weekly consumption frequencies and odds ratios (95 % confidence intervals) for consumption of high-sugar, refined and high-fat foods by parental education level for the total sample. Significant differences in mean frequency of consumption of the chosen foods between parental education groups were observed. The highest mean frequency of weekly consumption for fried potatoes, fruits with sugar and nuts, fried meat and fish, cold cuts, fast food, white bread, sugared beverages, snacks/desserts and chocolate/nut-based spread was observed in the low educational level category. Marked differences were observed for sugared beverages (17·5 (se 0·4) times/week in the low category v. 11·4 (se 0·2) times/week in the high category), snacks/desserts (9·3 (se 0·2) times/week in the low category v. 6·9 (se 0·1) times/week in the high category) and fruits with sugar and nuts (4·7 (se 0·2) times/week in the low category v. 2·5 (se 0·1) times/week in the high category). Odds ratio results show that participants in the low and medium parental education level categories had higher odds of more frequently consuming fried potatoes, fruits with sugar and nuts, fried meat and fish, sugared beverages and snacks/desserts (P < 0·001). Participants in the low parental education category had also higher odds of more frequently consuming fast food and chocolate/nut-based spread (P < 0·001). The largest odds ratio differences were found in the low category (reference category: high) for fruits with sugar and nuts (OR = 2·23; 95 % CI 1·92, 2·59), fried potatoes (OR = 2·00; 95 % CI 1·72, 2·31) and sugared beverages (OR = 2·01; 95 % CI 1·77, 2·37).
Table 3 Weekly consumption frequency (means and their standard errors), prevalence of high consumption, and odds ratios (95 % confidence intervals) for intake of high-sugar, refined and high-fat foods by classified parental education level; children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Reference group: high education.
Analysis of covariance model adjusted for gender, age and BMI category. Two-sided level of significance (P < 0·05): asignificant difference between low and medium; bsignificant difference between low and high; csignificant difference between medium and high.
OR and 95 % CI determined by logistic regression models. Variables included in the models were parental education, gender, age and BMI category. Two-sided level of significance: *P < 0.05, ***P < 0.001.
†p refers to the proportion of participants assigned to the highest consumption category.
‡Includes soft drinks, fruit juices and sugared milk.
Tables 4 and 5 show the weekly consumption frequencies and odds ratio (95 % confidence intervals) for consumption of low-sugar and low-fat foods and high-sugar, refined and high-fat foods, respectively, by parental education level and by participating country. The largest differences by parental education category were observed in Hungary for sugared beverages (22·5 (se 2·4) times/week in the low category v. 14·1 (se 0·4) times/week in the high category) and for white bread (13·9 (se 1·4) times/week in the low category v. 8·0 (se 0·2) times/week in the high category); in Belgium for water (9·7 (se 1·9) times/week in the low category v. 17·2 (se 0·3) times/week in the high category); and in Cyprus for snacks/desserts (11·0 (se 4·0) times/week in the low category v. 6·1 (se 0·2) times/week in the high category).
Table 4a Weekly consumption frequency (means and their standard errors), prevalence of high consumption, and odds ratios (95 % confidence intervals) for intake of low-sugar and low-fat foods by classified parental education level and country; children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Reference group: high education.
Analysis of covariance model adjusted for gender, age and BMI category. Two-sided level of significance (P < 0·05): asignificant difference between low and medium; bsignificant difference between low and high; csignificant difference between medium and high.
OR and 95 % CI determined by logistic regression models. Variables included in the models were parental education, gender, age and BMI category. Two-sided level of significance: *P < 0·05, ***P < 0·001.
†p refers to the proportion of participants assigned to the highest consumption category.
Table 4b Weekly consumption frequency (means and their standard errors), prevalence of high consumption, and odds ratios (95 % confidence intervals) for intake of low-sugar and low-fat foods by classified parental education level and country; children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Reference group: high education.
Analysis of covariance model adjusted for gender, age and BMI category. Two-sided level of significance (P < 0·05): asignificant difference between low and medium; bsignificant difference between low and high; csignificant difference between medium and high.
OR and 95 % CI determined by logistic regression models. Variables included in the models were parental education, gender, age and BMI category. Two-sided level of significance: *P < 0·05, ***P < 0·001.
†p refers to the proportion of participants assigned to the highest consumption category.
Table 5a Weekly consumption frequency (means and their standard errors), prevalence of high consumption, and odds ratios (95 % confidence intervals) for intake of high-sugar, refined and high-fat foods by classified parental education and country; children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Reference group: high education.
Analysis of covariance model adjusted for gender, age and BMI category. Two-sided level of significance (P < 0·05): asignificant difference between low and medium; bsignificant difference between low and high; csignificant difference between medium and high.
OR and 95 % CI determined by logistic regression models. Variables included in the models were parental education, gender, age and BMI category. Two-sided level of significance: *P < 0.05, ***P < 0.001.
†p refers to the proportion of participants assigned to the highest consumption category.
‡Includes soft drinks, fruit juices and sugared milk.
Table 5b Weekly consumption frequency (means and their standard errors), prevalence of high consumption, and odds ratios (95 % confidence intervals) for intake of high-sugar, refined and high-fat foods by classified parental education and country; children (n 14 426) aged 2 to 9 years from eight European countries, baseline survey of IDEFICS study, September 2007 to May 2008
Reference group: high education.
Analysis of covariance model adjusted for gender, age and BMI category. Two-sided level of significance (P < 0·05): asignificant difference between low and medium; bsignificant difference between low and high; csignificant difference between medium and high.
OR and 95 % CI determined by logistic regression models. Variables included in the models were parental education, gender, age and BMI category. Two-sided level of significance: *P < 0.05, ***P < 0.001.
†p refers to the proportion of participants assigned to the highest consumption category.
‡Includes soft drinks, fruit juices and sugared milk.
In the Hungarian sample, consumption frequencies for the pasta/noodles/rice and wholemeal bread categories followed the opposite trend to that in the whole sample, i.e. higher means in the low parental education level group. Similarly, in the Belgian sample, consumption of chocolate/nut-based spread followed an inverse direction compared with the whole group, i.e. higher frequency in the Belgian high parental education level group.
The largest odds ratio differences for intake of each food item among education level groups were observed in Germany (fruits, fried meat and fish, fast food), Belgium (vegetables, fresh meat and fish, white bread, wholemeal bread, water, plain unsweetened milk), Sweden (fried potatoes, chocolate/nut-based spread), Hungary (white bread, snacks/desserts), Spain (fruits with sugar and nuts) and Italy (sugared beverages, pasta/noodles/rice). As an exception, Hungarian and Swedish participants in the low parental education group had higher odds of more frequently consuming pasta/noodles/rice, wholemeal bread (Hungarian) and plain unsweetened milk (Swedish).
Discussion
The present study addressed the relationship between parental education level and the consumption frequency of obesity-related foods in their children. Our findings confirm such an association for a number of the investigated food groups. The intakes of vegetables, fruits, pasta/noodles/rice, wholemeal bread and water increased as education level increased; while intakes of fried potatoes, fruits with sugar and nuts, fried meat and fish, fast food, sugared beverages, snacks/desserts and chocolate/nut-based spread increased as educational level decreased. These trends were observed for the total sample and for most of the participating countries. It is noteworthy to mention that the magnitude of educational differences varied across the selected countries and that some of the observed country-specific differences might reflect cultural food specificities. Country-specific cultural norms on what is considered to be ‘healthy eating’ and gastronomic heritage may have a major impact on education-related disparities in food habits(Reference Margetts, Martinez and Saba25). For instance, pasta frequency of consumption in Italy was higher in the high parental education group, possibly reflecting the paramount importance of pasta in the traditional Italian gastronomy. The same applies to the case of chocolate in Belgium. Other examples, like bread consumption (e.g. wholemeal bread in the northern countries, white bread in the southern countries) and plain unsweetened milk (e.g. high consumption in Sweden and Estonia), seem also to be affected by traditional consumption.
Similarly to our findings, higher intakes of fruits and vegetables in children and adolescents with high SES have been reported in previous studies(Reference Abudayya, Stigum and Shi26–Reference Rasmussen, Krolner and Klepp30). Some studies have observed that the impact of SES is particularly strong for healthy foods, such as vegetables and fruits(Reference Blake, Wethington and Farrell31). These findings were reported in several countries with different cultural backgrounds, suggesting that fruit and vegetables are commonly considered as healthy. However, some other socio-economic differences in food intake have not been reported consistently (like for wholemeal bread, pasta, fish or fats), suggesting that these are more culturally dependent.
Previous studies have also focused on the socio-economic situation of parents, especially on maternal education, finding again positive associations between parental education and foods reducing the risk of obesity, like fruits and vegetables(Reference Klocke29). Education could provide an important socio-economic influence on health-related behaviour as it may increase the use of health-related information(Reference Laitinen, Rasanen and Viikari32). Although some other SES indicators, mainly occupational position and income, have been shown to have an impact on food intake(Reference Irala-Estevez, Groth and Johansson33–Reference Wagstaff and Watanabe37), parental education level, especially maternal education level, has been strongly related to children's dietary habits(Reference Cribb, Jones and Rogers14, Reference Nilsen, Krokstad and Holmen38, Reference Ebenegger, Marques-Vidal and Nydegger39) and to childhood overweight and obesity(Reference Lamerz, Kuepper-Nybelen and Wehle13, Reference Ruijsbroek, Wijga and Kerkhof40, Reference Moschonis, Tanagra and Vandorou41).
An important strength of the present study is its large sample size and international multicentric nature, which allowed us to investigate the research question in different cultural settings with a wider variety of food consumption patterns. Another important strength of the study is the strict standardized procedures followed during the data collection of the IDEFICS fieldwork(Reference Ahrens, Bammann and Siani16, Reference Ahrens, Bammann and de Henauw17) and the high quality control procedures carried out during the project, including plausibility checks implemented in the database and performed during data entry.
One of the major limitations of the study is the response rate. The whole survey programme involved complex logistics for participants and required the active involvement of parents, so that time constraints prevented some parents from participating. In addition, a selection bias cannot be ruled out as individuals without health problems or not having concerns about their children's health may be less motivated to take part in such a study. It is also known that participation is lower both in people with lower levels of education and in high-income groups(Reference Groves42). As we have no systematic information about non-participants, the direction of a possible bias cannot be predicted.
A second limitation of the study design is the fact that the sample selected within the IDEFICS study was not necessarily representative for each specific country and the results obtained by the participating centres cannot be generalized to the whole countries.
Another limitation is related to the use of the frequency of consumption assessment tool, which is based on proxy reports. Proxy reporting might be strongly related to the number of meals under parental control. Subsequently, the accuracy of the consumption frequencies reported by parents could differ between countries, as the number of meals consumed at home did differ between the participating countries. Some previous studies suggest that over-reporting of foods reducing the risk of obesity mainly takes place among individuals with higher levels of education, due to their greater knowledge about healthy diet, and therefore might tend to overstate the actual consumption, the known social desirability bias(Reference Irala-Estevez, Groth and Johansson33, Reference Hulshof, Brussaard and Kruizinga43). Although FFQ are not designed to accurately capture intakes, results of food consumption frequencies derived from the food frequency section of the CEHQ-FFQ gave reproducible estimates of the consumption frequency in the IDEFICS children(Reference Lanfer, Hebestreit and Ahrens21).
Conclusions
The present study showed a strong association of parental education level with the frequency of consumption of high-fat, high-sugar foods and products increasing the risk of obesity. These findings suggest that children of parents with a low educational level may be at higher risk of unhealthy eating. Therefore, the socio-economic determinants of food choice within families need to be addressed. It should be noted that the amount of differences, and not only the size of differences, in relation to disease outcome is of interest, and should be addressed in future research. The results of the present study should lead to more accurate targeting of intervention programmes for healthy eating promotion in childhood, in order to overcome social health inequalities. Special focus should be driven to undereducated parents and their children, in order to minimize this social health burden.
Acknowledgements
The present analysis was conducted as part of the IDEFICS study (http://www.idefics.eu), undertaken with financial support of the European Community within the Sixth RTD Framework Programme Contract No. 016181 (FOOD) and grant support for the IDEFICS study from the European Union. There are no competing interests. The authors’ contributions were as follows: J.M.F.-A., statistical analysis and manuscript writing; T.M., statistical analysis and critical revision of the manuscript; K.B., study design, statistical analysis and critical revision of the manuscript; A.H., critical revision of the manuscript; G.B., critical revision of the manuscript; S.S., critical revision of the manuscript; L.R., critical revision of the manuscript; G.E., critical revision of the manuscript; C.H., critical revision of the manuscript; E.K., critical revision of the manuscript; I.H., statistical analysis and critical revision of the manuscript; L.A.M., study design, statistical analysis and critical revision of the manuscript. The authors are grateful for the support provided by school boards, headmasters and communities, and thank the IDEFICS children and their parents for participating in this extensive examination. The information in this document reflects the authors’ views and is provided as is. No guarantee or warranty is given that the information is fit for any particular purpose.
